Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C409/00—Peroxy compounds
  • C07C409/02—Peroxy compounds the —O—O— group being bound between a carbon atom, not further substituted by oxygen atoms, and hydrogen, i.e. hydroperoxides
  • C07C409/04—Peroxy compounds the —O—O— group being bound between a carbon atom, not further substituted by oxygen atoms, and hydrogen, i.e. hydroperoxides the carbon atom being acyclic
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C407/00—Preparation of peroxy compounds
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P20/00—Technologies relating to chemical industry
  • Y02P20/50—Improvements relating to the production of bulk chemicals
  • Y02P20/54—Improvements relating to the production of bulk chemicals using solvents, e.g. supercritical solvents or ionic liquids

Definitions

• the invention relates to a process for preparing organic hydroperoxides.
• TBHP Tertiary-butyl hydroperoxide
• PO propylene oxide
• MTBE methyl tertiary-butyl ether
• the first step as described in the art to improve the selectivity and reduce decomposition concerns treatment of the reactor walls typically with sodium pyrophosphates as disclosed in US patent No. 3,816,540, or with sodium stannate.
• the inner reactor walls are already passivated by the manufacturer prior to delivery. This method is effective, as removing the sodium pyrophosphates lowers the selectivity, which may be restored upon renewed passivation.
• the invention provides a process for preparing organic hydroperoxides by oxidation of a hydrocarbon feed with molecular oxygen at supercritical conditions, which process is carried out in the presence of a separate liquid water phase that is present in an amount of 0.5 to 20% weight on the weight of the feed as a water film on the inner walls of the reactor vessel.
• the inventors found plain water to be able to shield the reactor walls, thereby preventing contact between the organic hydroperoxides and the reactor walls. Surprisingly, the decomposition is not brought about by metal ions transmigrating through the water film. Moreover, water and (Lewis) acids are known to catalyse the rearrangement of the organic hydroperoxides, which would have caused the skilled reader to believe more rather than less decomposition to occur.
• the water is present in an amount of 0.75 to 10% w/w, more preferably in an amount of 1.0 to 3.0% w/w.
• the preservation of the water film depends on the geometry of the reaction vessel and the manner (rate) of stirring, and it may be affected by addition of water during the process.
• the proper form and location of the rotor blades as well as manner of stirring may be determined without difficulty in a limited number of experiments or through suitable computer design.
• a further important variable is the density of the reaction mixture.
• the density of TBHP is lower than that of ethylbenzene hydroperoxide, making it easier to form a stable film to shield the inner reactor walls.
• the density of the reaction mixture may of course be varied through the use of solvents.
• the effect of enhanced selectivity does not continue indefinitely. If in the process the water film deteriorates due to water loss, as may occur in continuous reactions, then the water should be replenished. If not, a decrease in selectivity comparable to that of unpassivated reactor vessels may occur.
• the process of the invention is used for the preparation of organic hydroperoxides from alkanes, aralkanes and cycloalkanes, although alcohols and aldehydes may also be used (thus preparing peracids and the like).
• the process should be conducted at supercritical conditions, whereas the critical temperature should preferably not exceed 250 °C.
• the range of suitable starting compounds thus includes compounds such as (critical temperature in °C in brackets): isobutane (134.7); isopentane (187.8); 2-methylpentane (224.3); cyclopentane (238.6) and isopropanol (235).
• hydroperoxides from such like as cyclohexane (280.4); ethylbenzene (343.9); cumene (362.7) and 2-ethylnaphthalene (513.3) will be difficult, but not impossible.
• the process is conducted below 200 °C.
• the preferred starting compounds are isobutane and isopentane.
• Preferred reaction conditions are indicated in claims 5 and 6.
• the present autoxidation reaction is carried out at super-critical conditions, i.e., at such pressure and temperature conditions, that the hydrocarbon feed forms neither a liquid phase nor a gaseous phase, but rather a single dense phase.
• super-critical conditions require a pressure in excess of 36 bar and a temperature in excess of 135 °C. Oxidation of isobutane under super-critical conditions has been described in US patent No. 4,404,406, the contents of which is herewith incorporated by reference. Obviously, in case another feed is used different temperature and pressure conditions apply.
• Autoxidations are generally carried out with a surplus of feed over molecular oxygen and with only little conversion of the feed to avoid competing reactions to occur and decomposition of the organic hydroperoxides.
• the conversion of the hydrocarbon feed is in the range of 1 to 25%, based on the hydrocarbon feed. More suitably, the conversion is in the range of 5 to 15%.
• Decomposition may also be avoided by addition to the reaction mixture of an inorganic base such as any one of the hydroxides, carbonates, bicarbonates, phosphates, or pyrophosphates of the alkali metals or earth alkaline metals and the alkali metals of organic carboxylic acids, or by addition of an organic base, such as dimethyl amine , trimethylamine, triethylamine, dibutylamine, triethanolamine, piperidine, pyridine and tetraethylenepentamine.
• an inorganic base such as any one of the hydroxides, carbonates, bicarbonates, phosphates, or pyrophosphates of the alkali metals or earth alkaline metals and the alkali metals of organic carboxylic acids
• an organic base such as dimethyl amine , trimethylamine, triethylamine, dibutylamine, triethanolamine, piperidine, pyridine and tetraethylenepentamine.
• the amount of oxygen may be in the range of 10 to 30% mole on mole of the feed although more or less may be used. A ratio of 13 to 20 mole/mole is preferred.
• the oxygen may be supplied as air or as concentrated oxygen, but the preferred source of oxygen is pure oxygen.
• the process may be conducted batch-wise or in a continuous mode, either as a single reaction, or by conducting a plurality of such oxidation reactions.
• a process is for instance disclosed in US patent No. 4,408,081, using a cascade of reactors.
• a cascade of reactors is used, preferably in at least the last reactor of the cascade water is present.
• the process is conducted in a continuous manner, with residence times suitably in the order of 15 to 90 minutes, for instance in the order of 30 to 60 minutes. Residence times in batch reactors are comparable.
• the invention is illustrated by the following example(s).
• IB isobutane
• a gold-plated reactor has been used to study the IB oxidation in a supposed absence of wall effects.
• the gold-plating included everything inside the reactor, so walls, inlet tubes and stirrer.
• the gold-plating was applied in a galvanic way.
• the reactor was opened and cleaned (wiping with a tissue and rinsed with demineralised water, thereby removing the passivation).
• the blank experiment in absence of pyrophosphate provided a TBHP selectivity of 47 %mole.
• stirrer speed and direction have been varied. In absence of water, the stirrer speed does not influence the selectivity. However, in the presence of 3% w/w water, the TBHP/TBA ratio (w/w) increased from 2.8 to 3.6 with a stirrer speed going from 330 to 1180 rpm. At 330 rpm, the stirring direction also influences the TBHP/TBA ratio, but this is not the case at 1180 rpm.

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• Chemical & Material Sciences (AREA)
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• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

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Citations (4)

• 1998
  • 1998-11-12 EP EP98203816A patent/EP0916655B1/de not_active Expired - Lifetime

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